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S89E,F DIRECT SPARK IGNITION CONTROL MODULE
Measure Flame Current
The S89 provides ac power to the flame sensor which the
flame rectifies to direct current. If the flame signal back to the
S89 is less than 0.8 µA, the S89 will shut down the system.
To measure the flame current:
1. Connect a meter, set to the dc microammeter scale, in
series with the flame sensor as shown in Fig. 6. Use the
Honeywell W136 Test Meter or equivalent. Connect the
meter as follows:
a. Disconnect the sensor lead at the S89.
b. Connect the red (positive) meter lead to the S89
sense terminal.
c. Connect the black (negative) meter lead to the free
end of the sensor lead.
2. Restart the system and read the meter. The flame
sensor current must be at least 0.8 µA and steady.
68-0066—4
CHECK BURNER FLAME CONDITION
NOISY LIFTING FLAME
CHECK FOR:
• HIGH GAS PRESSURE
• EXCESS PRIMARY AIR
BURNER
WAVING FLAME
CHECK FOR:
• POOR DRAFT
• EXCESS DRAFT
• HIGH VELOCITY OR
INSTALL SHIELD IF NECESSARY.
SMALL BLUE FLAME
CHECK FOR:
• CLOGGED PORTS OR
• WRONG SIZE ORIFICE
LAZY YELLOW FLAME
CHECK FOR
LACK OF AIR FROM:
GOOD RECTIFYING FLAME
1 IN. (25.4 MM)
1/4 TO 1/2 IN. (6.4 TO 12.7 MM)
Fig. 7. Check burner flame condition.
10
3. If the meter reads less than 0.8 µA or reading is
unsteady, recheck points under Check Flame Sensor
and Igniter, above.
FLAME SENSOR CURRENT CHECK–USE µA SCALE
VALVE
VALVE (GND)
24V
24V (GND)
SENSE
GND (BURNER)
Fig. 6. S89 flame current measurement.
OR DRAFT
SECONDARY AIR
ORIFICE FILTER
• DIRTY PRIMARY
AIR OPENING
• LARGE PORTS
OR ORIFICES
M18055
TO
SENSOR
W136 (OR EQUIV.)
MULTIPURPOSE METER
DISCONNECT
WIRE FROM
SENSE
TERMINAL
BLACK
(–)
RED (+)
0.8 µA DC MINIMUM
(AND STEADY)
M19840
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